1. Field of the Invention
The present invention relates to a display device and a manufacturing method thereof, and particularly, to a display device having a display panel on which a plurality of display pixels each having a light emitting element whose carrier transporting layer is formed by coating a liquid material including a carrier transporting material, are arrayed in two dimensions, and a manufacturing method thereof.
2. Description of the Related Art
Recently, as a display device of an electronic apparatus such as a portable telephone, a portable music player, etc., there is known a display device on which mounted is a display panel (organic EL display panel), on which organic electroluminescence elements (hereinafter abbreviated as “organic EL elements”) are arrayed in two dimensions. Particularly, an organic EL display panel adapted to an active matrix drive system has extremely superior characteristics to liquid crystal display devices widely spread, in that the display response speed is high, there is no dependency on view angles, high luminance, high contrast, and high preciseness of the display quality, etc. are available, and a compact and light body can be obtained because no backlight or light guide plate is needed unlike a liquid crystal display device.
As well known, an organic EL element roughly has an element structure formed of an anode (positive) electrode, an organic EL layer (light emitting function layer), and a cathode (negative) electrode which are sequentially stacked on one surface of a glass substrate or the like, and emits light (excitation light) based on the energy that is produced when holes and electrons injected into the organic EL layer are recombined in this layer, when a positive voltage is applied to the anode electrode and a negative voltage is applied to the cathode electrode in a manner that the organic EL layer exceeds a light emitting threshold. Organic EL elements are roughly classified into a low molecular type and a high molecular type, according to organic materials (positive hole transporting materials and electron-transporting light emitting materials) for forming a positive hole transporting layer (positive hole injecting layer) and an electron-transporting light emitting layer (light emitting layer), which make up the organic EL layer.
In a case where a low-molecular organic material is used, the manufacturing process of the organic EL element generally requires vapor deposition and therefore needs a mask in some case to prevent the low molecular material from being vapor-deposited on other areas than the anode electrode because it is necessary to selectively form a thin organic film of this low molecular type only on the anode electrode in a pixel forming region. Consequently, the low molecular material inevitably is deposited also on the surface of the mask, producing a great loss of material in the manufacturing process, making the manufacturing process inefficient.
On the other hand, in a case where a high-molecular organic material is used for the organic EL element, since an ink jetting method (liquid drop jetting method), a nozzle printing method (liquid flow jetting method), or the like can be used as a wet film forming method, the solution of the organic material can selectively be coated only on the anode electrode or a specific region including the anode electrode, providing a merit that a thin organic EL layer (a positive hole transporting layer and an electron-transporting light emitting layer) can be formed through an efficient manufacturing process with little material loss.
Further, some organic EL display panels of the high molecular type are known to have a panel structure with a continuous partitioning wall, which is formed to project upward from an insulating substrate such as a glass substrate or the like on which display pixels are arrayed and which is formed between pixel forming regions in which these display pixels are formed respectively, in order to define these pixel forming regions, and to prevent a phenomenon that light emitting colors, are mixed beyond the respective display pixels with light emitting materials of different colors from adjoining pixel forming regions mixing into other regions when liquid materials (solutions) made of high-molecular organic materials are coated. An organic EL display panel with such a partitioning wall is explained in, for example, Unexamined Japanese Patent Application KOKAI Publication No. 2001-76881.